Remarks

It is recommended to avoid using this method unless really necessary, since it will effectively disable client caching of generated icons, and will also cause the same icon to be rendered multiple times, when used multiple times on a single page.

An alternative is to create a separate php file whose purpose is only to serve identicons. Let the file accept query string parameters for icon size and value, and serve the icon with a really high max-age in the Cache-Control header.